This invention relates to brakes for magnetic tape transports, and particularly to dynamic brakes for the driving motors thereof.
The stopping of a magnetic tape transport requires that the reels, and sometimes the capstan, be braked in order to prevent the tape coming off the supply reel from forming or "throwing" loops and catching in the mechanism. To avoid the use of cumbersome and expensive mechanical brakes, various schemes have been attempted for operating the take-up and supply reel motors themselves to produce the desired braking effect.
U.S. Pat. No. 3,906,299 discloses such a system in which the take-up reel upon being switched off causes the supply reel to be energized in reverse to brake the tape.
U.S. Pat. No. 3,809,329 discloses a system in which the motors charge condensers during normal operation, and the condenser is then discharged to energize the supply reel motor in reverse during stopping to brake the tape.
U.S. Pat. No. 3,895,277 teaches braking only for a capstan motor, but mentions that it is possible to short the armature leads during the stopping period, causing the motor to act as its own brake.
Accordingly, it is an object of the present invention to provide means for operating the motors of a tape transport as effective brakes during stopping or upon power failure to the transport.